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#ifndef MESSAGE_FILTERS__CHAIN_HPP_
#define MESSAGE_FILTERS__CHAIN_HPP_

#include <vector>
#include <memory>

#include "message_filters/simple_filter.hpp"
#include "message_filters/pass_through.hpp"

namespace message_filters
{
/**
 * \brief Base class for Chain, allows you to store multiple chains in the same container.  Provides filter retrieval
 * by index.
 */
class ChainBase
{
public:
  virtual ~ChainBase() {}

  /**
   * \brief Retrieve a filter from this chain by index.  Returns an empty shared_ptr if the index is greater than
   * the size of the chain.  \b NOT type-safe
   *
   * \param F [template] The type of the filter
   * \param index The index of the filter (returned by addFilter())
   */
  template<typename F>
  std::shared_ptr<F> getFilter(size_t index) const
  {
    std::shared_ptr<void> filter = getFilterForIndex(index);
    if (filter) {
      return std::static_pointer_cast<F>(filter);
    }

    return std::shared_ptr<F>();
  }

protected:
  virtual std::shared_ptr<void> getFilterForIndex(size_t index) const = 0;
};
typedef std::shared_ptr<ChainBase> ChainBasePtr;

/**
 * \brief Chains a dynamic number of simple filters together.  Allows retrieval of filters by index after they are added.
 *
 * The Chain filter provides a container for simple filters.  It allows you to store an N-long set of filters inside a single
 * structure, making it much easier to manage them.
 *
 * Adding filters to the chain is done by adding shared_ptrs of them to the filter.  They are automatically connected to each other
 * and the output of the last filter in the chain is forwarded to the callback you've registered with Chain::registerCallback
 *
 * Example:
\verbatim
void myCallback(const MsgConstPtr & msg)
{
}

Chain<Msg> c;
c.addFilter(std::make_shared<PassThrough<Msg> >());
c.addFilter(std::make_shared<PassThrough<Msg> >());
c.registerCallback(myCallback);
\endverbatim

 *
 * It is also possible to pass bare pointers in, which will not be automatically deleted when Chain is destructed:
\verbatim
Chain<Msg> c;
PassThrough<Msg> p;
c.addFilter( &p);
c.registerCallback(myCallback);
\endverbatim
 *
 */
template<typename M>
class Chain : public ChainBase, public SimpleFilter<M>
{
public:
  typedef std::shared_ptr<M const> MConstPtr;
  typedef MessageEvent<M const> EventType;

  /**
   * \brief Default constructor
   */
  Chain()
  {
  }

  /**
   * \brief Constructor with filter.  Calls connectInput(f)
   */
  template<typename F>
  explicit Chain(F & f)
  {
    connectInput(f);
  }

  struct NullDeleter
  {
    void operator()(void const *) const
    {
    }
  };

  /**
   * \brief Add a filter to this chain, by bare pointer.  Returns the index of that filter in the chain.
   */
  template<class F>
  size_t addFilter(F * filter)
  {
    std::shared_ptr<F> ptr(filter, NullDeleter());
    return addFilter(ptr);
  }

  /**
   * \brief Add a filter to this chain, by shared_ptr.  Returns the index of that filter in the chain
   */
  template<class F>
  size_t addFilter(const std::shared_ptr<F> & filter)
  {
    FilterInfo info;
    info.add_func = std::bind(
      (void (F::*)(const EventType &)) & F::add, filter.get(), std::placeholders::_1);
    info.filter = filter;
    info.passthrough = std::make_shared<PassThrough<M>>();

    last_filter_connection_.disconnect();
    info.passthrough->connectInput(*filter);
    last_filter_connection_ = info.passthrough->registerCallback(
      typename SimpleFilter<M>::EventCallback(
        std::bind(&Chain::lastFilterCB, this, std::placeholders::_1)));
    if (!filters_.empty()) {
      filter->connectInput(*filters_.back().passthrough);
    }

    size_t count = filters_.size();
    filters_.push_back(info);
    return count;
  }

  /**
   * \brief Retrieve a filter from this chain by index.  Returns an empty shared_ptr if the index is greater than
   * the size of the chain.  \b NOT type-safe
   *
   * \param F [template] The type of the filter
   * \param index The index of the filter (returned by addFilter())
   */
  template<typename F>
  std::shared_ptr<F> getFilter(size_t index) const
  {
    if (index >= filters_.size()) {
      return std::shared_ptr<F>();
    }

    return std::static_pointer_cast<F>(filters_[index].filter);
  }

  /**
   * \brief Connect this filter's input to another filter's output.
   */
  template<class F>
  void connectInput(F & f)
  {
    incoming_connection_.disconnect();
    incoming_connection_ = f.registerCallback(
      typename SimpleFilter<M>::EventCallback(
        std::bind(&Chain::incomingCB, this, std::placeholders::_1)));
  }

  /**
   * \brief Add a message to the start of this chain
   */
  void add(const MConstPtr & msg)
  {
    add(EventType(msg));
  }

  void add(const EventType & evt)
  {
    if (!filters_.empty()) {
      filters_[0].add_func(evt);
    }
  }

protected:
  virtual std::shared_ptr<void> getFilterForIndex(size_t index) const
  {
    if (index >= filters_.size()) {
      return std::shared_ptr<void>();
    }

    return filters_[index].filter;
  }

private:
  void incomingCB(const EventType & evt)
  {
    add(evt);
  }

  void lastFilterCB(const EventType & evt)
  {
    this->signalMessage(evt);
  }

  struct FilterInfo
  {
    std::function<void(const EventType &)> add_func;
    std::shared_ptr<void> filter;
    std::shared_ptr<PassThrough<M>> passthrough;
  };
  typedef std::vector<FilterInfo> V_FilterInfo;

  V_FilterInfo filters_;

  Connection incoming_connection_;
  Connection last_filter_connection_;
};
}  // namespace message_filters

#endif  // MESSAGE_FILTERS__CHAIN_HPP_
